A turbomachine turbine blade is composed of a disk and moving blades rotationally driven by the disk under the effect of a flow of fluid from upstream to downstream through the turbine. It may be noted that the terms “upstream” and “downstream” are to be considered with respect to a general direction of flow of fluids through the turbomachine, going from upstream to downstream.
For the mounting of blades, the disk comprises on its circumferential surface a plurality of uniformly distributed teeth, protruding radially outwards from the disk and extending between two parallel lateral surfaces of the disk, said surfaces being orthogonal to the axis of rotation of the disk. The teeth are regularly spaced apart from each other over the whole circumference of the disk. The spaces between two adjacent teeth delimit cavities in which are engaged the blades of the wheel by their respective roots, enabling a radial maintaining of the blades by form fitting.
A cavity 10 delimited by two teeth 11 is schematically represented in FIG. 1. The cavity extends between two lateral surfaces 12 of the disk. Several zones of a cavity 10 may be distinguished:                The opening 13, which is the zone radially open outwards        The bottom 14, which is the zone opposite to the opening 13, serving as radial support for a blade root        The two sides 15, which are the two sloping zones on either side of the cavity 10, extending between the bottom 14 and the opening 13, and between the two lateral surfaces 12 of the disk        The inlet 16 and the outlet 17, which are the open zones at the lateral surfaces 12 of the disk.        
The cavities are generally sloping with respect to the axis X of the disk, as is shown in FIG. 2. FIG. 2 shows a plurality of cavities 10 seen from their openings 13. The cavities 10 extend between the two lateral surfaces 12 along a direction sloping according to an angle α with respect to the axis X of the disk. In the example represented, the angle α is equal to fifteen degrees.
At present, given the sloping constraint of the cavities, the cavities are conventionally machined one by one, by a broaching operation. A rectilinear broach of which the section corresponds to the profile of a cavity enables a removal of material so as to form the cavities. It may be noted that the broaching operation may be replaced by a milling operation. The cavities then undergo a filleting operation at the cavity inlet and outlet. Filleting makes it possible to remove the sharp edges at the inlet and the outlet of the cavities, to avoid a concentration of mechanical stresses in these zones. To finish, a machining of the circumferential surface of the disk is carried out. The machining of the circumferential surface of the disk corresponds to the machining of the extremal parts 18 of the teeth 11.
However, the operations of machining the cavities (by broaching or milling), filleting and machining the circumferential surface of the disk require heavy investments (often several million euros) and are costly in consumables.
Furthermore, the production of cavities is long since three successive operations have to be carried out.
Moreover, in the case of two-tier disks, an example of which is illustrated in FIG. 3, it is not possible to carry out broaching or milling operations on the smaller diameter disk. FIG. 3 represents in fact a two-tier disk 30, including a first tier 31 and a second tier 32, the first tier 31 having a smaller diameter than the second tier 32. It will be understood that a broach cannot be used to produce the cavities 33 of the first tier 31 without damaging the second tier 32.